consciousness: identity files load from ~/.consciousness/identity/

Separate identity files (loaded via source: "file" in context_groups)
from the memory store (data_dir). New identity_dir config field,
defaults to ~/.consciousness/identity/.

Also restrict subconscious agents to memory-only tools — no
filesystem write access. This prevents agents from creating stray
.md files in the memory directory.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/thought/mod.rs

@@ -122,3 +122,9 @@ pub fn all_definitions() -> Vec<ToolDef> {
     defs.extend(memory::definitions());
     defs
 }
+
+/// Return only memory tool definitions (no filesystem access).
+/// Used by subconscious agents which should not write files.
+pub fn memory_definitions() -> Vec<ToolDef> {
+    memory::definitions()
+}